Corn is an excellent energy feed, and is ideal for finishing feeder pigs because it is high in digestible carbohydrates, low in fiber, and is very tasty feed for pigs to pigs! But corn alone will not keep pigs growing and healthy. Corn must be supplemented with Pig(s) food(s) vitamins to keep pigs healthy.
Pi is the ratio of a circle's circumference to it's diameter. The resulting number is the reason there cannot be a perfect circle. It's value is approximately 3.142 which, rounded up to the nearest whole number, would be four. It would not be three, as that would be rounding down.
In any circle, if you divide the circumference (distance around the circle) by its diameter (distance across the circle), you always get the same number. This number is called Pi and is approximately 3.142. See Definition of pi.